Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accounts receivable, allowance for doubtful accounts	$ 5,642	$ 2,494
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	70,261,481	69,582,669
Treasury stock, shares (in shares)	7,564,874	3,567,575